Sectional ingot molds are known in the prior art. U.S. Pat. No. 496,736 issued May 2, 1893 to C. Hodgson and U.S. Pat. No. 1,224,277 issued May 1, 1917 to F. Clarke, are examples of prior art sectional mold constructions. U.S. Pat. Nos. 354,742 issued Dec. 21, 1886 to J. Sabold and British Pat. No. 13446 of A. D. 1900 in the name of Stephen Appleby, et al and entitled "Improvements in or Connected with Ingot Molds", disclose sectional mold arrangements embodying means for relieving stress on the fastening bolts thereof due to the expansion of the molten metal. However, such prior art sectional molds have not alway been satisfactory, due at least in part to oftentimes leakage of molten metal occurring between the mold sections during the pouring of the molten metal into the mold cavity and subsequent solidification of the metal, or due to the complexity and/or costs of such arrangements.
H. S. Lee and Amos E. Chaffee in U.S. Pat. No. 1,584,954 issued May 18, 1926 identified Permanent Mold Distortion and its attempted control by using thermally responsive insert elements to effect control of a permanent mold leaking molten metal along the parting line and to avert distortion or a bowing action of the mold by placing higher or lower coefficient of expansion metals in position in the mold to resist the inward or outward movement of the mold thus directly effecting the casting being formed and produced by the permanent mold.
U.S. Pat. No. 158,696 to Foster et al discloses a sectional mold in conjunction with spring-loaded bolts to provide for lateral expansion of the mold sections relative to one another during the expansive force of the molten metal poured into the mold.
In the aforementioned U.S. Ser. Nos. 3,093 and 78,447 of applicant Bowman, there is disclosed sectional ingot molds having fastener means for connecting mold wall sections together to form a mold cavity, and providing for automatic compensation, including a delayed faster rate of expansion for reducing stresses, and also including memory, to allow for expansion and retraction of the mold assembly sections when molten metal is poured into the ingot mold and during the subsequent cooling of the ingot, while aiding in sealing the mold sections from leakage of molten metal during the pouring and subsequent cooling of the ingot in the mold. The prior art cited in said U.S. Bowman applications is incorporated herein by reference.
In British Pat. No. 1,380,726, published Jan. 15, 1975 there is disclosed a sectional ingot mold having separate corner members adapted to mate into concave recesses in the mold wall sections for attempting to relieve the stress resulting from the temperature gradient existing across the side wall sections upon pouring of molten metal into the mold. A strap extending around the wall sections serves to hold the latter in assembled relation in one embodiment, and coiled spring strips at the mold corners exerting constant force are utilized in another embodiment.
British Pat. No. 1,464,075 published Feb. 9, 1977 discloses a liquid cooled chill-casting sectional mold which includes split clamping rings holding the mold parts together, with Belleville type disc spring means acting on the extremities of the split clamps, for pressing the extremities toward one another. However, there are no teachings concerning pre-loading or what such pre-loading should accomplish.
British Pat. No. 1,240,893 published July 28, 1971 discloses a slab mold having a bottom wall movable upwardly relative to the side walls of the mold at a rate which will exert a pressure on the metal equal or greater than the ferrostatic pressure, thereby attempting to prevent a rupture of the skin of a solidifying slab and escape of molten metal from the slab's interior.
None of the prior art molds, in applicants' opinion, is optimumly operable when exposed to thermal, elastic and ferrostatic stresses resulting from the pouring of molten metal into a sectional mold in the formation of ingots, such as for instance steel ingots, in the manner of applicants' arrangement.